Women who took a fertility drug called Clomid don’t have any higher risk of breast cancer, even 30 years later, than women who did not, a new study shows.
The findings should reassure women worried that they would pay down the road for having taken the drug, which stimulates the production of eggs.
“Overall, our data show that use of fertility drugs does not increase breast cancer risk in this population of women, which is reassuring,” says Louise Brinton, who heads research on hormone-related cancer at the National Cancer Institute.
In 2009, another team of researchers showed the drugs also did not appear to raise the risk of ovarian cancer.
It is a hard risk to study, because women who are infertile have a higher risk of cancer, so it’s been difficult to show whether the drugs raise the risk. Brinton’s study, published in the journal Cancer Epidemiology, Biomarkers and Prevention, shows women who did not conceive despite taking fertility drugs had nearly twice the risk of breast cancer compared with women who did not take fertility drugs.
And women who took 12 or more cycles of Clomid, known generically as clomiphene, also had a small increased risk, the study of 9,800 women showed.
“The observed increase in risk for these small subsets of women may be related to persistent infertility rather than an effect of the medications,” said Brinton. “Nevertheless, these findings stress the importance of continued monitoring of women who are exposed to fertility drugs.”
Doctors now limit clomiphene to three to six cycles at doses far lower than what were given in the past.
“Given the high doses of drugs received by our study participants and the lack of large increases in breast cancer risk many years after exposure, women previously exposed to such drugs should be reassured by these findings,” said Brinton.
First published April 2 2014, 9:01 PM
Maggie Fox is senior health writer for NBC News and TODAY, writing top news on health policy, medical treatments and disease.
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She's a former managing editor for healthcare and technology at National Journal and global health and science editor for Reuters based in Washington, D.C. and London.
She's reported for news agencies, radio, newspapers, magazines and television from across Asia, the Middle East, Africa and Europe covering news ranging from war to politics and, of course, health and science. Her reporting has taken Maggie to Lebanon, Syria and Libya; to China, South Korea, Thailand, the Philippines and Pakistan; to Bosnia, Croatia and Serbia and to Ireland and Northern Ireland and across the rest of Europe.
Maggie has won awards from the Society of Business Editors and Writers, the National Immunization Program, the Overseas Press Club and other organizations. She's done fellowships at Harvard Medical School, the National Institutes of Health and the University of Maryland.